A weapons scanner was a scanning device attached to a door or any specific section of a passageway. It could be used as a way to ensure that dangerous objects are not taken past a certain point. They were specifically seen to be used on Cardassian military installations, such as the space stationTerok Nor.

In 2369, Miles O'Brien used the weapons scanner on one of the docking ports as a way of disabling one of the Hunters that had boarded Deep Space 9. The device was shown to be extremely effective at blocking passage through the port while any type of powered weapon was being worn, and the power setting could be ramped up to a point where the discharge from the device could knock a person unconscious. (DS9: "Captive Pursuit")

The device appeared to operate in much the same way as a force field, which scanned the person as they passed the field.

Chief Miles O'Brien's phaser activates the weapon detectors in one of Deep Space 9's airlocks